Global Sea Ice Trends
About Sea Ice Data
The sea ice data you can find here is collected every day by the National Snow and Ice Data Center (NSIDC). Sea ice extent is divided into the northern and southern hemispheres, and a global measurement which is just the total of both hemispheres. It’s measured as the total area (in millions of square kilometers) that sea ice covers. Anomaly values are based on how different an ice measurement is on a given date compared with the long-term average for that same day. Positve values indicate more ice than normal, and negative values indicate less ice than normal. The farther a value is from 0, the less normal it is.
Monthly Sea Ice Extent
Monthly Sea Ice Anomalies
Monthly Sea Ice Anomalies Comments
From looking at the anomaly plot, it seems like global anomalies are mostly driven by changes in the northern hemisphere. Based on simple linear models, this rings true, as anomalies in the northern hemisphere explain ~64% of variation in global anomalies, while the southern hemisphere anomalies only explains around 28% of global variation> This makes sense when we look at the annual trends in sea ice extent, where global ice extent is mostly driven by declining sea ice in the northern hemisphere.
Annual Trends in Sea Ice Extent
Annual Trends in Sea Ice Comments
This plot shows the average sea ice extent for each year. Based on simple linear regression models, global sea ice decreased on average by ~49,000 square kilometers each year from 1979-2021. Sea ice on the northern hemisphere decreased on average by ~54,000 square kilometers. Based on these trends, if mean annual sea ice trends continued at the same rate as they have since 1979, we would predict that sea ice on average will disappear from the northern hemisphere by the year 2210, and globally / in the southern hemisphere, by the year 2468.
Barplot of Hemishperic Sea Ice
Barplot of Hemishperic Sea Ice Comments
This plot shows the same data as the first plot, but using stacked bars instead for easier monthly comparison of southern and northern hemisphere sea ice extent.
Sea Ice Duration
Annual Duration of Expanding and Receding Sea Ice
Surprisingly, unlike Minnesota lakes, the duration of sea ice expansion and recession in either the northern or southern hemisphere hasn’t really changed over the last 30 years. However, even though durations haven’t changed, we’ve shown from other plots that sea ice is expanding less and receding more when it does happen.
Northern Hemisphere Sea Ice Durations
Southern Hemisphere Sea Ice Durations
Sea Ice, Temperature, and Sea Level
Relationship between Sea Ice and Temperature
These two temperature plots show the significant effect that global mean temperature change has had on the extent of global sea icem and, even more, on the presence of anomalies in global sea ice.
Global Sea Ice Extent and Temperature
Global Sea Ice Anomalies and Temperature
Sea Ice and Temperature Comments
This plot shows the significant effect that even a small decline in global sea ice has with a rise in global sea level. While their are certainly other effects at play that contribute to a rise in sea level, such as global temperature, it’s interesting nonetheless. It’s important to note that because of data obtained, this plot represents sea ice and levels during the month of March.
Global Sea Ice and Sea Level
Global Sea Ice and Sea Level Comments
This plot shows the significant effect that even a small decline in global sea ice has with a rise in global sea level. While their are certainly other effects at play that contribute to a rise in sea level, such as global temperature, it’s interesting nonetheless. It’s important to note that because of data obtained, this plot represents sea ice and levels during the month of March.